More than two-thirds of Saudi citizens working for one of the kingdom’s largest employers have been sacked, amid an ongoing economic crisis sparked by low oil prices.

Saudi daily Al Watan reported on Monday that 12,000 of 17,000 Saudi employees had been fired at the Binladin Group construction firm.

The Saudis had been employed as engineers, administrators and inspectors, according to Watan.

The newspaper cited an unnamed company official who said that in addition to the Saudi sackings, 77,000 out of 200,000 foreign workers had been fired and given permanent exit visas to leave the kingdom.

However, Watan reported on Friday that at least 50,000 of the expatriate workers were refusing to leave Saudi Arabia because they have not been paid for at least four months.

The unpaid workers have been holding daily protests at the company’s offices, and on Saturday footage uploaded to YouTube showed at least seven buses set on fire by protesters at Binladin offices in Mecca province.

Local authorities are now investigating the fires, which were extinguished without causing any fatalities.

Another protest on Friday saw five laid off Binladin workers reportedly injured when a company official ran them over with a car, local papers reported.

A spokesman for Binladin told Bloomberg on Monday that all those laid off had been paid “full compensation” and dismissed reports of angry workers.

“Adjusting the size of our manpower is a normal routine, especially whenever projects are completed or near completion,” the spokesman said.

“Most of the released jobs had initially been recruited for contracted projects with specific time frame and deliverables.”

The company didn’t rule out further sackings, but said that it would honour salary commitments “in case further manpower is released”.

The Binladin Group, which was established in 1931 by the father of the late al-Qaeda leader Osama Bin Laden, is one of Saudi Arabia’s largest employers and it has been responsible for large construction projects including building towers in the capital Riyadh, and universities and airports in the western port city of Jeddah.

But the company has reportedly been suffering from debts of up to $30bn and it has been engaged in a series of pay disputes with workers, which in March led to protests outside their offices in Riyadh.

Binladin may also be feeling the pinch because of a catastrophe at one of its projects last year, when a crane in the holy city of Mecca collapsed and killed 107 people.

The incident prompted the government to suspend the company from future contracts, and led to an investigation by the finance ministry into its existing state projects.

Saudi Arabia has been forced to cut its government spending as oil prices, which account for the majority of the kingdom’s income, have plummeted by up to 70 percent in two years.